1) Occurrence
of metals and non metals :-
Out of the 92
naturally occuring elements 70 are metals and about 22 are nonmetals. Some elements
show properties of both metals and non metals. They are called metalloids. Only
some metals like gold, silver, platinum etc are found in the free state. Most
metals are found in the combined states as oxides, sulphides, carbonates,
silicates etc. Some non metals are found in the free state like helium, neon,
argon etc. and some are found in free and combined states like sulphur,
phosphorus etc.
2) Metallurgy
:-
Metallurgy:- is science of
extraction of metals from their ores and their purification.
Minerals:- are naturally
occuring substances containing one or more elements or their compounds.
Ore:- is a mineral from
which one or more metals can be extracted profitably.
Metallurgical
processes:-
consists of three main steps.
They are :- i) Concentration of the ore
ii)
Reduction
iii) Refining
Concentration of the
ore:- is the removal of impurities from the ore.
Reduction:- the
process of obtaining the metal from its compound.
Refining:- is the
process of purification of the impure metals to obtain the pure metal.
3) Physical properties
of metals and non metals :-
Metals :
1.
Metals are solids (except mercury).
2.
Metals are hard (except sodium, potassium etc.
3.
Metals have metallic lustre.
4.
Metals have high melting points and boliling points.
5.
Metals are malleable ( can be made into thin sheets).
6.
Metals are ductile (can be made into thin wires).
7.
Metals are good conductors of heat and electricity.
8.
Metals are sonorus (produces sound).
Non metals
1.
Non metals may be solids, liquids or gases.
2.
Non metals which are solids are brittle (diamond is the
hardest).
3.
Non metals do not have lustre some have a dull luster.
4.
Non metals have low melting points.
5.
Non metals are not malleable.
6.
Non metals are not ductile.
7.
Non metals are bad conductors of heat and electricity
(except graphite).
8.
Non metals are not sonorus.
4) Chemical
properties of metals and non metals :-
a) Reaction with
oxygen :-
Metals react with oxygen to form metallic
oxides. These oxides are
basic oxides because they react with water
to form bases.
Eg. Magnesium burns in air to form
magnesium oxide. Magnesium
reacts with water to form magnesium
hydroxide.
2 Mg + O2 --> 2 MgO
MgO + H2O --> Mg(OH)2
Non metals react with oxygen to form
non metallic oxides. These
oxides are acidic oxides because they react
with water to form
acids.
Eg. Sulphur burns in air to form sulphur
dioxide. Sulphur dioxide
reacts with water to form sulphurous acid.
S + O2 --> SO2
SO2 + H2O --> H2SO3
b) Reaction with
water :-
Metals react with water to form metal hydroxides and hydrogen.
Eg. Sodium reacts with water to form sodium
hydroxide and
hydrogen.
2 Na + 2 H2O --> 2 Na OH + H2
Magnesium reacts with water to form magnesium hydroxide
and
hydrogen.
Mg + H2O --> Mg(OH)2 + H2
Non metals do not react with water.
c) REACTION
WITH ACIDS:-
Metals react with acids to form metallic
salts and hydrogen.
Eg. Zinc reacts with dilute hydrochloric acid
to form zinc chloride
and hydrogen.
Zn + 2 HCl --> ZnCl2 + H2
Most non metals do not react with acids. Some non metals like sulphur
reacts with concentrated nitric acid to forn sulphur dioxide, nitrogen dioxide
and water.
S + 4 HNO3 --> SO2 + 4 NO2 +2
H2O
d) Metals replace
metals :-
A more reactive metal replaces a
less reactive metal from its salt solution.
Eg. Magnesium replaces copper from copper
sulphate solution to form magnesium sulphate and copper.
Mg + CuSO4 --> MgSO4 + Cu
Zinc replaces copper from copper
sulphate solution to for zinc
sulphate and copper.
Zn + CuSO4 --> ZnSO4 + Cu
Iron replaces copper from copper
sulphate solution to form iron sulphate and copper
Fe + CuSO4 --> FeSO4 + Cu
Based on the reactivity of metals, they
can be arranged in the decreasing order of their activity.
5) Activity
series of metals :-
The arranging of metals in the decreasing order of their reactivity
is called activity series of metals.
Potassium
Sodium
Magnesium
Aluminium Decreasing
Zinc order of
Iron reactivity
Lead
Copper
Silver
Gold
6) Noble
metals :-
Metals like gold,
silver, platinum etc. retain their lustre because they do not react with air,
water or acids. So they are called
noble metals.
Gold dissolves in aqua regia. Aqua regia is a
mixture of concentrated nitric acid and concentrated hydrochloric acid in the
ratio 1:3.
Pure is 24 carat gold. It is very soft and
cannot be used for making ornaments. So it is mixed with some silver or copper
to make it hard.
7) Uses of
metals :-
Iron :- is used for making
pins, nails, nuts, bolts, tools, machines, construction of buildings, bridges
etc.
Aluminium :- is used for making
utensils, wires, furniture, parts of aircrafts, vehicles, machines, for packing
food and medicines etc.
Copper :- is used for making
wires, vessels, electric gadgets etc.
Gold :- is used for making
jewellery, coins medals etc
Silver :- is used for making
jewellery. Coins, medals etc.
Platinum :- is used for making
jewellery, electric gadgets,plugs in vehicles etc.
Sodium :- compounds are used
as common salt, chemicals etc.
Calcium :- compounds are used
for making cement, glass etc.
8) Uses of
non metals :-
Sulphur :- is used for making
sulphuric acid, salts of
metals etc.
Oxygen :- is used for respiration by
living things, burning
of fuels etc.
Nitrogen :- is used for making ammonia
which is used for
making fertilizers.
Hydrogen :- is used for making ammonia which
is used
for making fertilizers, as fuel in rockets,
for welding etc.
Chlorine :- is used to kill germs in water.
Iodine :- is used as tincture iodine
which is an antiseptic.
An alloy is a homogeneous mixture of a metal with other metals or non metal.
Alloy Constituents Uses
Steel iron, carbon construction of tools,
machines,
tanks,
vehicles, ships, rails, building,
bridges, dams etc.
Stainless steel iron,
chromium utensils, cutlery,
surgical
instruments etc.
Brass copper, zinc utensils, handicrafts musical
instruments
etc.
Bronze copper, tin statues, medals, bells
ornaments etc.
Alnico iron, aluminium making of magnets
nickel, cobalt
Duralium aluminium, copper making utensils, pressure cookers,
magnesium, parts of vehicles, aircrafts etc.
manganese
10) Corrosion
:-
The surface of some metals gets corroded
when exposed
to moist air for a long time. This is called
corrosion.
Prevention of corrosion of metals :-
The corrosion of metals can be prevented
by:-
i) Applying oil or grease.
ii) Applying paint
iii)
Galvanisation ( coating of metals with
non corrosive
metals like
zinc)
iv) Electroplating (
coating of metals with non corrosive
metals like
chromium tin by passing
electricity)
v) Alloying ( Eg. When iron is alloyed with
chromium
and nickel, it
forms stainless steel which
is resistant to
corrosion)
11) Activity
to show that air and water are necessary for
rusting of iron :-
rusting of iron :-
Take three test tubes and put one iron nail
in each. Put some anhydrous calcium chloride in one test tube to absorb
moisture. Pour some boiled water from which dissolved oxygen has been removed
in the second test test tube. Pour some water in the third test tube. Cork the
three test tubes and leave it for 3 – 4 days. It is seen that the nail in the
first and second test tubes have not rusted. The nail in the third test tube
has rusted.
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